Circuit interrupter



May 20. 1941 c. DlcKlNvsoN ETAL 2,242,905

CIRCUIT INTERRUFTER Patented VMay 20, 1941 UNITED STATES PATENT OFFICE CIRCUIT INTEEBUPTER Robert C. Dickinson and Robert B. Nau, Wilkinsburg, Pa., signora to Westinghouse Electric Manufacturing Company, East Pittsburgh, Pa., a corporation of Pennsylvania Application March 11, 1939, Sel'ill No. 261,240

(Cl. 20G-147) l2 Claims.

This invention relates to improvements in circuit interrupters and more particularly to arc extinguishing devices for circuit interrupters of the air break type.

In the application of L. R. Ludwig, Serial No. 216,884, filed July l, 1938 and assigned to the assignee of this application is shown and described an arc extinguishing structure for circuit interrupters of the air break type in which arc extinction is accomplished by the lateral movement of an established arc toward the closed ends of a series of tapered notches formed in spaced plates of insulating material. Lateral movement of the arc. as set forth in the afore said Ludwig application, is obtained by a magnetic eld self-induced in plates of magnetic material disposed adjacent the arc receiving notches. This magnetic field is also relied upon to produce a blast of un-ionized gas through the arc while the arc is held substantially immovable against the closed ends of the slots or notches in the plates of insulating material.

The principal object of our invention is to improve the operation of arc extinguishing devices of the aforesaid type whereby electrical circuits of materially higher voltages may be successfully interrupted. This has been accomplished by rendering the arc extinguishing struc-v ture more effective throughout its entire length, thereby increasing the interrupting capacity in terms of volts interrupted per unit length of structure.

A more specific object of the invention is to provide stationary arc terminal means at the opposed ends of an arc extinguishing device of the aforesaid type and cooperating arc transfer means for establishing an arc between the terminal means so as to render the entire arc extinguishing structure more effective in bringing about are extinction.

The further object of the invention is to render arc extinguishing devices of the type above referred to more capable of interrupting higher voltages by materially reducing the vaporization of metal at the arc terminals and by preventing deposit of metallic particles upon the insulating structure between the arc terminals.

Other objects and advantages relate to the structural arrangement of. our improved arc extinguishing structure and will appear more fully in the following description when taken in connection with the accompanying drawings in which:

Figure 1 is a fragmentary view of a circuit interrupter showing the arc extinguishing device of our invention in section;

Fig. 2 is a top view of the arc extinguishing device shown in Fig. l;

Fig. 3 is a sectional view of the arc extinguishing device of our invention taken along the line III-III of Fig. 1; and

Fig. 4 is a sectional view of the arc extinguishing device taken along the line IV-IV of Fig. 1.

Referring to the drawings, the reference number 5 designates a panel upon which is mounted a stationary contact assembly 1. The contact assembly 1 includes an arcing contact 8 mounted for limited pivotal and sliding movement about the pin Il in the assembly. Adapted to cooperate with the arcing contact 9 is a movable arcing contact i3 carried by a contact arm il which may be mounted for pivotal movement to the open and closed position in a manner as more specifically shown in the copending application of L. R. Ludwig, et al. No. 216,708, filed June 30, 1938 and assigned to the assignee of this application, now Patent No; 2,214,471 dated September 10, 1940.

An arc established upon the separation of contacts 9 and I3 is adapted to be extinguished by .an arc extinguishing device I'l, the lowerv portion of which partially encloses the contact structure. The arc extinguishing device I1 comprises a back support plate I9 of insulating material and a front support plate 2i also of insulating material between which are disposed a plurality of plates 2l of insulating material. The plates 23 are preferably made of a material that is substantially free from substance which gives off gas when acted upon by an arc, such as asbestos board, quartz, soap stone, or titanium oxide.` Cold molded compositions, as for example a product known as artificial porcelain comprising 30% talc, 2% feldspar, and 68% clay may also be used. In general, all materials which are refractory in nature and have the requisite mechanical strength are suitable for this purpose.

Each oi' the plates 23, as shown more clearly in Figs. 3 and 4, is provided with a V-shaped notch 25 extending inwardly from the lower end thereof. The upper ends of the notches 2l are staggered as shown at 2l in Figs. 3 and 4. The upper ends of the plates 23 as shown in Figs. 3 and 4 have trapezoidal cut-out portions at the corners thereof for the reception of U-shaped plates 29 of magnetic material. The plates 20 are disposed in endwise abutting relation with the plates 23 and thus provide a relatively narrow yoke across the top of the plate and legs joining the yoke extending downwardly on either side of the narrow slot portion 21. The purpose of plates 23 of magnetic material will appear more Vfully hereinafter. The -plates 23 of refractory material as well as the plates 29 of magnetic material which form extensions to the former plates are held in spaced relation with respect to each other by suitable spacing bars 3|, also preferably of refractory material, disposed along the side edges of the respective plates.

In order to render the stack of plates 23 more capable of withstanding high voltage, suitable barrier plates 32 of insulating material may be employed disposed between the upper ends of the spacers 3| so as to form extensions on at least each alternate plate 29 of magnetic material.

At each end of the stack of plates 23 is an insulating plate 33 also preferably of refractory material that is similar to the plates 23 with the exception that it is of considerably greater length and has a V-shaped notch 35 therein having considerably less depth than the notches 25 in the plates 23. Disposed adjacent to the back support plate |9, and spaced from the plate 33 by spacing members 36 is an arcing plate 31 of conducting material such as copper. The lower end of the arclng plate 31 is provided with a bifurcated offset extension 39 which serves as an arc receiving terminal in a manner to be more fully described hereinafter. A second arcing plate 4| is disposed adjacent the front support plate 2| and is also spaced from the front plate 33 of insulating material by spacing members 36. The lower end of the arcing plate 4| is provided with a laterally extending terminal or horn 43 to which is secured one end of a flexible shunt 45, the other end of which is attached to the moving contact arm |5.

Both the back and front support plates i9 and 2| are recessed for the reception of a bar 41 of magnetic material for the purpose of aiding arc movement upwardly along the arclng plates 31 and 4|. The entire plate assembly, that is`, the structure between the front and back support plates L9 and 2|, is held in the assembled position by a pair of tie bolts 49 covered with an insulating sleeve The tie bolts 45 may extend, if desired, through the panel 5 for the purpose of securing the arc extinguishing device I1 thereto. Each side of the plate assembly is preferably provided with a cover plate 52 secured to the back and front support plates |3 and 2| by screws, as shown.

From the foregoing structure it will be apparent that the V-shaped notches 25 in the plates 23 as well as the V-shaped notches 35 in the plates 33 provide an arc passage of considerable length having a V-shaped cross-section and extending `between the arcing plates 31 and 4|. This arc passage extends upwardly into the constricted slot portions 21 in the plates 23, a substantial distance beyond the closed end of the notches 35 in the plates 33.

It will also be observed that the spacing members 3| provide free venting passages 53 for the passage of arc gases upwardly between the respective plates, thus freely venting the arc passage defined by the respective notches in the plates of refractory material.

The operation of the device is as follows: Upon separation of the contacts 3 and I3 the arcing contact 3 moves to the position shown by the dotted lines in Fig. 1 with the upper end thereof closely adjacent to the stationary extension 33 of the arcing plate 31. The movable contact arm i5 pivots to the right and moves to the dotted line position shown in Fig. l, thus drawing an arc, the right hand end of which is quickly transferred to the lateral extension 43 of the arc plate 4|.

Due to the natural bowing and looping of the arc, the magnetic reaction set up thereby quickly causes the arc to move upwardly at the left hand end onto the extension 39 and at the right hand end onto the extension 43 and then to the respective arcing plates 31 and 4|. Since the arclng plate 4| is connected yby the flexible shunt 45 to the movable contact arm |5, the loop circuit is maintained and the arc moves upwardly into the entrance portion of the slots or notches 25 and 35. Upon entering the notches 25 and 35, upward movement of the arc is further facilitated by the magnetic reaction set up by the magnetic bar members 41 disposed in back of each of the arcing plates 31 and 4|. After the arc enters the slots 25, movement of the arc is principally effected toward the closed end thereof by the magnetic reaction self-induced in the U-shaped plates 29 of magnetic material. The magnetic action which causes lateral movement of the arc is sufiicient to move the arc against the closed ends of the slots 25 but is not strong enough to cause substantial bowing or looping of the arc between the plates 23 with the particular spacing employed between the plates.

As more specifically set forth in the aforesaid application of L. R. Ludwig, the plates 23 of insulating material may vary from 1A; to 1/4" in thickness and may be spaced from each other from 1/8 to 1/4. Also as more fully explained in the aforesaid application, the magnetic action which causes the arc to be moved upwardly also produces a blast of un-ionized gas laterally through the arc, which blast of gas is freely vented from the arc stream into the spaces 53 y between the plates 23.

Arc extinction is thus accomplished by the joint action of constricting the arc in the relatively confined portions 21 of the slots in the plates 23 and the cross blast produced by the magnetic action moving the arc.

We have discovered that the use of arcing plates in a conventional manner at each .end of a stack of plates of the form herein shown materially lowered the interrupting ability of the arc extinguishing device, particularly due to the fact that an arc playing upon a conventional arclng plate or horn vaporizedthe material thereof and rendered the arc path more conducting. We have overcome this dimculty by the provision of a shield of the form shown at 33 in which the slot 35 is of less depth than the slots 25 in the intermediate plates 23. Thus as the arc moves upwardly, the ends thereof first engage the closed end of the slot 35. Immediately thereafter the portion of the arc on either side of the plate 33 moves upwardly, the one side 'along its respective arclng plate and the other side in the form of a loop which extends through the aro passage defined by the narrower slotlike portions 21 of the plates 23. The end portions of the arc carried upwardly respectively on the arclng plates 31 and 4| are subjected to a predetermined lengthening as a result oi' the strong magnetic action set up by the magnetic bar member 41 and also the gas blast produced by the magnetic means moving the arc. When this -end portion of the arc has reached a predetermined length, it can no longer maintain itself andY restrikes to the arcing plate at a point substantially opposite to the upper end of the notch 35 in the plate 33. In order to facilitate movement of the terminal ends of the arc between the arcing plates 31 and ll and their respective plates 33 of insulating material, a somewhat greater spacing is required between these plates than between the plates 23.

'I'his action of lengthening the terminal ends of the arc and the restriking of the arc at a different point on the arcing plate takes place with such rapidity that a cold cathode terminal is formed on the arcing plates 31 and 3| thereby preventing the vaporization of the contact metal of which these arcing platesare composed. The fact that the slot 35 in the plates 33 is of less depth than the slots in the plate 33, constitutes the plates 33 as shield plates which prevent any metal particles which may be formed due to the restriking of the arc to the arcing plates from being carried into the arc stream along the arc path as defined by the narrow slot portions 21 in the plates 23.

The relatively large area of the arcing plates 31 and 4i is effective to produce a uniform electrostatic field of relatively low intensity between the plates which assists in maintaining a more uniform distribution of voltage between the arcing plates following arc extinction, Furthermore, the area of the plates 31 and Il is large as compared with the area of the plates 29 of magnetic material disposed in spaced relation between the arcing plates 31 and 4i. Thus, the arcing plates 31 and 4I also serve as an electrostatic shield with respect to the plates 29 of magnetic material, thereby preventing an unbalance in voltage across the entire stack of plates as a result of capacity to ground from the plates 23 of magnetic material.

Although we have shown and described a speciflc arc extinguishing device it is to be understood that the same is for the purpose of illustration and that changes and modifications may be made by those skilled in the art without departing from the spirit and scope of the appended claims.

We claim as our invention:

l. In a circuit interrupter, means of insulating material defining an arc passage of considerable length having a V-shaped cross section, a terminal conductor adjacent each end of said arc passage. means for establishing an arc between said terminal conductors in the enlarged portion of said arc passage, means for moving the arc laterally between said terminal conductors to the restricted side of said arc passage, vent passages for said arc passage communicating with at least the restricted side thereof, and means for causing the ends of the arc to be moved over their respective terminal conductors at a rate to provide a cold cathode terminal at each conductor, said vent passages being dimensioned to enable said arc to play in the restricted portion of said are passage without bowing or looping into the vent passages.

2. In a circuit interrupter, an arc extinguishing device comprising a plurality o! spaced plates of insulating material, a terminal conductor adjacent each outer plate of insulating material. said plates of insulating material having tapered slots extending inwardly from one of their ends, said slots providing an arc path between said terminal conductors, means for establishing an arc between said terminal conductors, means for moving said arc laterally to the closed ends of said slots with the ends thereof in engagement with said terminal conductors, said plates of insulating material being spaced a distance from each other to prevent substantial looping of the arc between said plates, each terminal conductor being spaced a predetermined distance from its adjacent plate of insulating material for causing the ends of said arc to be moved rapidly over the surface of said terminal conductors while the intermediate portion of the arc is held substantially immovable at the closed ends of said slots.

3. In a circuit interrupter. an arc extinguishing device comprising a plurality of spaced plates of insulating material, a plate of conducting material adjacent cach outer plate of insulating material, said plates of insulating material having V-shaped slots extending inwardly from one cf their ends, said slots providing an arc path between said plates of conducting material, means for establishing an arc between said plates of conducting material, and magnetic means for moving said arc laterally between said plates of conducting material to the closed ends of said slots, each plate of insulating material adjacent a plate of conducting material being spaced a predetermined distance from its respective plate of conducting material and having a slot of less depth than the slot in the intermediate plates of insulating material for causing the ends of the arc to play over the surface of said plates of conducting material with such rapidity to provide cold cathode terminals on said plates of conducting material.

4. In a circuit interruptor, means of insulating material defining an arc passage of considerable length having a V-shaped cross section, an arcing plate of conducting material disposed adjacent each end of said arc passage, means for establishing an arc between said arcing plates in the enlarged portion of said arc passage, magnetic means for moving the arc laterally between said arcing plates to the restricted side of said arc passage, vent openings leading through said meansof insulating material to at least the restricted side of said arc passage, said vent openings being dimensioned and disposed with respect to vthe restricted side of said arc passage' to cause said arc to play in the restricted portion of the arc passage without looping into said vent openings, and means including a member of magnetic material disposed on the outside of each arcing plate for causing the ends of said arc to be moved over saidarcing plates at a rate to prevent the formation of hot cathode terminals thereon.

5. In a circuit interrupter, an arc-extinguishing device comprising a plurality of plates of insulating material, means spacing said plates a predetermined distance from each other to provide venting spaces therebetween, an arcing plate of conducting material adjacent each outer plate of `insulating material, said plates of insulating material having elongated tapered notches therein to provide an arc path between said arcing plates, meansfor establishing an arc in said notches between said arcing plates, and plate means of magnetic material disposed only adjacent the closed ends of the notches of a plurality of said plates of insulating material to provide an intense magnetic field for moving the arc laterally between said arcing plates towards the closed ends of said notches, said arcing plates having an area sufficient to cause between and across the plate means of magnetic material.

6. In a circuit interrupter, an arc extinguishing device comprising a plurality of spaced plates of insulating material, a plate of conducting material adjacent each outer plate of insulating material, said plates of insulating material having V-shaped slots extending inwardly from one oi their ends, said slots providing an arc path between said plates of conducting material, means for establishing an arc between said plates of conducting material, and magnetic means for moving said arc laterally between said plates of conducting material to the closed ends of said slots, and for causing a blast of un-lonized gas to ilow laterally through said arc while the arc is held against the closed ends of said slots, each plate of insulating material adjacent a plate of conducting material having a slot of less depth than the slots in the intermediate plates of insulating material to prevent metallic particles produced at the arc terminals from being deposited on said intermediate plates.

7. In a circuit interrupter, an arc-extinguishing device comprising, a plurality of plates of insulating material arranged in spaced relation to provide a stack having vent passages therethrough; an arcing plate of conducting material disposed in spaced relation with respect to each end of said stack, said stack having a tapered notch extending inwardly from one end of each said plates to provide an arc path of considerable length between said arcing plates, means for establishing an arc between said arcing plates, magnetic means for moving the arc laterally between said arcing plates to the closed end of said notches, and a shield plate of insulating material disposed in spaced relation between each arcing plate and said stack, each shield plate having a notch extending inwardly from one end thereof of depth less than said notches in said stack of plates to prevent metallic particles produced at the arc terminals from being carried on to the plates in said staclr said meansfor moving the arc causing a blast or' gas to flow through the arc, the vent passages and the spaces between said arcing and shield plates.

8. The method of extinguishing an electric arc playing between spaced terminals, comprising restricting an intermediate portion of the arc in cross section, holding said intermediate portion in substantially one position while restricted, moving at least one terminal end of the arc over the surface of its terminal while the intermediate portion of the arc is held in said position and subjecting at least the intermediate portion of said arc to a blast of un-ionized gas.

9. The method of extinguishing an electric arc playing between spaced terminals, comprising restricting a substantial intermediate portion of the arc in cross section, holding said restricted intermediate portion in a predetermined position, moving at least one terminal end of said ya more uniform distribution of voltage therearc over the surface of its terminal at a rate to produce a cold cathode on said terminal, and subjecting at least the restricted intermediate portion of said arc to a blast of un-ionized gas.

10. The method of extinguishing an electric arc playing between spaced terminals, comprising moving the arc laterally between said terminals, restricting at least a substantial intermediate portion thereof in cross section, holding said restricted intermediate portion in a substantially immovable position, moving at least one terminal end of the arc over the surface of its terminal, and finally subjecting the arc to a lateral blast oi un-ionized gas.

11. In a circuit interrupter, means of insulating material dening an arc passage having a V-shaped cross section, an arcing plate of conducting material disposed adjacent each end of said arc passage, means for establishing an arc between said arcing plates in the enlarged portion of said arc passage, means for moving the arc laterally between said arcing plates to the restricted side of said arc passage, vent openings extending from at least the restricted side of said arc passage through said means of insulating material, and a barrier member of insulating material disposed adjacent each end of said means of insulating material, said barrier members extending a substantial distance into the arc passage and being spaced a distance from their respective arcing plates to enable the ends of the arc to oscillate along the arcing plates and to prevent the metallic vapors and particles produced adjacent the arc terminals from being driven into the constricted portion of the arc passage.

12. In a circuit interrupter, an arc extinguising device comprising a plurality of plates of insulating material, means spacing said plates a predetermined distance from each other to provide venting spaces therebetween, an arcing plate of conducting material adjacent each outer plate of insulating material, said plates of insulating material having elongated tapered notches therein to provide an arc path between said arcing plates, means for establishing an arc in said notches between said arcing plates, and means of metallic material disposed only adjacent the closed ends of the notches of a plurality of said plates of insulating material to provide a magnetic field which increases in intensity as the arc approaches the closed ends of said notches for moving the arc laterally between said arcing plates towards the closed end of said notches, and a shield plate of insulating material disposed between each arcing plate and the outer notched plate of insulating material, said shield plates extending into the arc path provided by said notches to prevent metallic vapors and particles produced at the arc terminals from being carried into the arc path provided by said ta-.

pered notches.

' ROBERT C. DICKINSON.

ROBERT H. NAU. 

